400mH

Description

Competitors run once around a 400m track and clear ten evenly-spaced hurdles in the process. They start from blocks placed in staggered positions and run in lanes.
A reaction time – measured by sensors in the starting pistol and on the blocks – of less than 0.1 is deemed a false start and all the runners are recalled. After one false start anyone responsible for a subsequent false start is disqualified immediately. A runner can also be disqualified if he or she steps out of their designated lane.

Men jump hurdles that are 36in (91.4cm) high; women negotiate 30in (76.2cm) barriers. The hurdles are knocked down easily if touched, which allows the athlete to continue even if he or she collides with them.